Regarding pf a/c succession certificate

A/c holder deceased, her nominee were father and mother (with 50% each). Father got expired, now only mother is alive. Deceased was married. Can mother claim PF a/c amount 100 % as one of the nominee is expired? Or she need succession certificate of deceased? Deceased is having one child only, age of 13 and her husband also expired. This is the only child deceased. Pls suggest how to claim? Also who's succession certificate is required?